我如何知道我的Google地图当前所在的实际比例？ [英] How can I know the actual scale that my Google maps is currently in?
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问题描述
我的网站上有Google地图（v3），我想知道当前缩放的缩放比例。问题是用户可以改变它的缩放比例，因此可以改变比例。
我需要的信息是我的地图的实际宽度（以公里为单位）。我知道我可以使用界限......但还有其他方法吗？
谢谢！
解决方案
所以你可以调用map.getBounds（）。然后，您可以使用 google.maps.geometry.spherical 类，如 computeDistanceBetween 或 computeLength 。像这样的东西我认为应该给你你需要的东西：
<！DOCTYPE html>
< html>
< head>
< title>< / title>
< meta name =viewportcontent =initial-scale = 1.0，user-scalable = no/>
< style type =text / css>
html {height：100％}
body {height：100％;保证金：0; padding：0}
#map_canvas {height：100％}
< / style>
< script type =text / javascriptsrc =http://maps.googleapis.com/maps/api/js?sensor=false&libraries=geometry>< /脚本>
< script type =text / javascript>
函数initialize（）{
var homeLatlng = new google.maps.LatLng（51.476706,0）; //伦敦
var myOptions = {
zoom：15，
center：homeLatlng，
mapTypeId：google.maps.MapTypeId.ROADMAP
};
var map = new google.maps.Map（document.getElementById（map_canvas），myOptions）;
$ b google.maps.event.addListener（map，'bounds_changed'，function（）{
//找出地图边界：
var bounds = map .getBounds（）;
//从中得到NE和SW角的坐标
var NE = bounds.getNorthEast（）;
var SW = bounds.getSouthWest （）;
//从中找出纬度和经度
var lat1 = NE.lat（）;
var lat2 = SW.lat（）;
var lng1 = NE.lng（）;
var lng2 = SW.lng（）;
//使用水平距离的坐标构造新的LatLngs lng1和lng2
var horizontalLatLng1 = new google.maps.LatLng（lat1，lng1）;
var horizontalLatLng2 = new google.maps.LatLng（lat1，lng2）;
/ /使用垂直距离的坐标构造新的LatLng n lat1和lat2
var verticalLatLng1 = new google.maps.LatLng（lat1，lng1）;
var verticalLatLng2 = new google.maps.LatLng（lat2，lng1）;
//计算水平距离
var horizontal = google.maps.geometry.spherical.computeDistanceBetween（horizontalLatLng1，horizontalLatLng2）;
//垂直计算距离
var vertical = google.maps.geometry.spherical.computeDistanceBetween（verticalLatLng1，verticalLatLng2）;
//圆到公里到1dp
var horizontalkm = convertMetresToKm（horizontal）;
var verticalkm = convertMetresToKm（vertical）;
alert（horizontalkm +'km horizontal，'+ verticalkm +'km vertical'）;
}）;
function convertMetresToKm（meters）{
return Math.round（meters / 1000 * 10）/ 10; //以km为单位的距离舍入为1dp
}
google.maps.event.addDomListener（window，'load'，initialize）;
< / script>
< / head>
< body>
< div id =map_canvas>< / div>
< / body>
< / html>
I have a Google map (v3) on my site and I want to know what scale is my current zoom. The thing is that the user can change it's zoom so the scale can change.
The information I need is the actual width in kilometers of my map. I know I can use Bounds... but is there any other way? I really don't want to use Bounds.
Thank you!
解决方案
So you can call map.getBounds(). Then you can use functions on the google.maps.geometry.spherical class like computeDistanceBetween or computeLength. Something like this I think should give you what you need:
<!DOCTYPE html>
<html>
<head>
<title></title>
<meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
<style type="text/css">
html { height: 100% }
body { height: 100%; margin: 0; padding: 0 }
#map_canvas { height: 100% }
</style>
<script type="text/javascript" src="http://maps.googleapis.com/maps/api/js?sensor=false&libraries=geometry"></script>
<script type="text/javascript">
function initialize() {
var homeLatlng = new google.maps.LatLng(51.476706,0); // London
var myOptions = {
zoom: 15,
center: homeLatlng,
mapTypeId: google.maps.MapTypeId.ROADMAP
};
var map = new google.maps.Map(document.getElementById("map_canvas"), myOptions);
google.maps.event.addListener(map, 'bounds_changed', function() {
// find out the map's bounds:
var bounds = map.getBounds();
// from that, get the coordinates for the NE and SW corners
var NE = bounds.getNorthEast();
var SW = bounds.getSouthWest();
// from that, figure out the latitudes and the longitudes
var lat1 = NE.lat();
var lat2 = SW.lat();
var lng1 = NE.lng();
var lng2 = SW.lng();
// construct new LatLngs using the coordinates for the horizontal distance between lng1 and lng2
var horizontalLatLng1 = new google.maps.LatLng(lat1,lng1);
var horizontalLatLng2 = new google.maps.LatLng(lat1,lng2);
// construct new LatLngs using the coordinates for the vertical distance between lat1 and lat2
var verticalLatLng1 = new google.maps.LatLng(lat1,lng1);
var verticalLatLng2 = new google.maps.LatLng(lat2,lng1);
// work out the distance horizontally
var horizontal = google.maps.geometry.spherical.computeDistanceBetween(horizontalLatLng1,horizontalLatLng2);
// work out the distance vertically
var vertical = google.maps.geometry.spherical.computeDistanceBetween(verticalLatLng1,verticalLatLng2);
// round to kilometres to 1dp
var horizontalkm = convertMetresToKm(horizontal);
var verticalkm = convertMetresToKm(vertical);
alert(horizontalkm + ' km horizontal, ' + verticalkm + ' km vertical');
});
}
function convertMetresToKm(metres) {
return Math.round(metres / 1000 *10)/10; // distance in km rounded to 1dp
}
google.maps.event.addDomListener(window, 'load', initialize);
</script>
</head>
<body>
<div id="map_canvas"></div>
</body>
</html>
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